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Re: Not-ing out ports
From: Jason Wallace <jason.r.wallace () gmail com>
Date: Mon, 13 May 2013 11:06:29 -0400

On Mon, May 13, 2013 at 10:19 AM, Lay, James <james.lay () wincofoods com>wrote:

Guessing you’ll want the !25 on both ends since it’s bidirectional:****

** **

alert tcp !25 any <> any !25****

**



Isn't that first !25 in the IP address field? Wouldn't it be...

alert tcp any !25 <> any !25



 **

James****

** **

*From:* John Wiltberger [mailto:johwiltb () gmail com]
*Sent:* Monday, May 13, 2013 5:01 AM
*To:* snort-sigs () lists sourceforge net
*Subject:* [Snort-sigs] Not-ing out ports****

** **

So I have a question.  When dealing with bi-directional signatures (I
know, they aren't ideal in the least, but sometimes you can't help who
develops your signatures), if you choose to not-out a port (as in !<port
number>), does snort run a boolean OR on the traffic (as in 'if source port
!= <port number OR destination port != <port number>)?

Reason is, I have a signature that's header is 'alert tcp any any <> any
!25', yet it is still alerting off of traffic over port 25.  I'm sorry if
these seems confusing, I can't think of a better way of stating this.  Any
thoughts?****


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------------------------------------------------------------------------------
Learn Graph Databases - Download FREE O'Reilly Book
"Graph Databases" is the definitive new guide to graph databases and 
their applications. This 200-page book is written by three acclaimed 
leaders in the field. The early access version is available now. 
Download your free book today! http://p.sf.net/sfu/neotech_d2d_may
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